Rock picker

ABSTRACT

Apparatus for picking rocks, or similar articles, from the ground including a frame supported for forward movement over the ground, and an elongated rotatable digging head having a plurality of laterally-spaced ground-penetrating teeth thereon. An elongated rotatable clearing head is mounted above the digging head and includes a plurality of laterally-spaced teeth which are positioned to sweep between the digging teeth to remove picked articles therefrom. The digging head is mounted for vertical movement on the frame and is adjustable between a lowered groundpenetrating position and a position raised above the ground. A conveyor adjacent the digging and clearing heads receives articles cleared from the digging head and moves them away from the head and to a crusher in the apparatus.

United States Patent 11 1 Bliss ROCK PICKER [76] inventor: Jon P.Bliss,l263l NE. 9th Place,

Bellevue, Wash. 98005 [22] Filed: June 3,1971 21 Appl. No; 149,601

[ June 19, 1973 Primary ExaminerAntonio F. Guida Atxorney-Kolisch,Hartwell & Dickinson [57] ABSTRACT Apparatus for picking rocks, orsimilar articles, from the ground including a frame supported forforward movement over the ground, and an elongated rotatable digginghead having a plurality of laterally-spaced ground-penetrating teeththereon. An elongated rotatable clearing head is mounted above thedigging head and includes a plurality of laterally-spaced teeth whichare positioned to sweep between the digging teeth to remove pickedarticles therefrom. The digging head is mounted for vertical movement onthe frame and is adjustable between a lowered ground-penetratingposition and a position raised above the ground. A conveyor adjacent thedigging and clearing heads receives articles cleared from the digginghead and moves them away from the head and to a crusher in theapparatus.

13 Claims, 3 Drawing Figures PAIENIED JUN! 9 I973 INVENTOR MAZZZa iii?PATENTED JUN! 9 Ian same or 2 Jon P. Bliss 1 Rock PICKER This inventionrelates to apparatus for picking rocks or similar articles from theground.

A general object of the invention is to provide novel apparatus which isoperable rapidly and efficiently to pick rocks or similar articles fromthe ground.

More specifically, an object is to provide such novel apparatus whichincludes a rotatable digging head having a plurality oflaterally-spaced, ground-penetrating digging teeth thereon for pickingarticles from the ground, and a rotatable clearing head having aplurality of laterally-spaced clearing teeth thereon which arepositioned to sweep between the digging teeth to clear picked articlesfrom the digging head.

Another object is to provide such novel apparatus in which the clearinghead is yieldably biased toward the digging head, which permits theclearing head to be urged away from the digging head should an articlebe picked and raised by the digging head which is too large to beaccommodated by the normal spacing between the two heads. Such mountingof the clearing head prevents large rocks from wedging between coactingteeth on the digging and clearing heads, which otherwise may causedamage to the apparatus.

Yet another object is to provide novel apparatus for picking rocks orsimilar articles from the ground, which includes a rotatable digginghead having a plurality of laterally-spaced digging teeth thereonarranged in multiple, circumferentially spaced rows extendingsubstantially parallel to the axis of the rotation of the head, and aclearing head adjacent the digging head and rotatable about an axissubstantially paralleling the axis of the digging head, the clearinghead having a plurality of laterally-spaced clearing teeth arranged inmultiple, circumferentially-spaced rows extending substantially parallelto the axis of the clearing head. The clearing and digging heads in suchapparatus are driven for rotation in opposite directions and theclearing teeth are positioned to pass between the digging teeth. Theclearing head has fewer rows of teeth than does the digging head, andthe two are driven for rotation in predetermined timed relationship,whereby successive rows of clearing teeth are moved through appropriatearcs between successive rows of digging teeth to sweep picked articlestherefrom. With this construction the clearing teeth are rotated fasterthan the digging teeth and such produces a sweeping action to cleararticles from the digging teeth.

Yet another object is to provide such novel apparatus in which thedigging teeth are arcuate, having forwardly facing surfaces which areconcave in the direction of rotation of the digging head. This permitsarticles picked by the digging teeth to be raised from the ground andover the central axis of the digging head. In such apparatus theclearing head is mounted above the digging head and the clearing teethsweep picked articles from the digging head as such articles are raisedabove the central axis of the digging head.

These and other objects and advantages will become more fully apparentas the following description is read in conjunction with the drawingswherein:

FIG. 1 is a side view of apparatus constructed according to theinvention;

FIG. 2 is an enlarged side view of a forward section of the apparatuswith portions broken away; and

FIG. 3 is a top plan view of the forward section of the apparatus shownin FIG. 2, with portions broken away.

Referring now to the drawings, and first more specifically to FIG. 1, at10 is indicated generally apparatus constructed according to anembodiment of the invention for picking rocks, or similar articles, fromthe ground. In general terms, the apparatus includes a main frame 12supported for powered movement over the ground by wheels 14. Mounted onthe forward end of the frame, at the left in FIG. 1, is a rotatabledigging head 16 operable to pick rocks or similar articles from theground, a rotatable clearing head 18 for clearing picked articles fromdigging head 16, and a conveyor 20 for receiving articles cleared fromthe digging head and for conveying them upwardly and rearwardly awayfrom the digging head. Conveyor 20 is operable to carry rocks receivedfrom the digging head to a primary crusher 24 which is operable to breakthe rocks into smaller sections, from which they are then passed to asecondary crusher 26 which is operable to break them into still finersections. The crushed rock then may be discharged onto the ground in itsreduced state or it may be transferred to another vehicle fortransporting elsewhere.

Describing now digging head 16, and referring specifically to the topplan view of FIG. 3, wherein a central portion of clearing head 18 hasbeen broken away, the digging head includes an elongated central shaft30 which extends transversely of the apparatus. Opposite ends of shaft30 are journaled for rotation in the forward ends of a pair of laterallyspaced elongated arms 32. The rear ends of arms 32 are journaled atpoints 36 on the forward end of frame 12.

A plurality of identical digging elements 40 are secured to shaft 30 inlaterally spaced relation. Referring to FIGS. 1 and 2, each diggingelement 40 has five dig ging teeth thereon, indicated generally at 40a,40b, 40c, 40d, and 40s. Each tooth, and referring specifically to tooth40a illustrated in FIG. 2, is arcuate, having a concave surface 40ffacing in one direction and terminating at the outer end of the tooth ina digging point 40g. The teeth are substantially equally spacedcircumferentially about shaft 30. The digging elements on shaft 30 aresubstantially aligned with each other in a direction extending axiallyof the shaft, with the digging teeth thereon thus being disposed in aplurality of circumferentially spaced rows extending substantiallyaxially of the digging head. A pair of laterally spaced disks 50 aresecured to shaft 30 adjacent its opposite ends and outwardly fromopposite ends of digging elements 40.

Clearing head 18, above digging head 16, includes an elongated shaft 54journaled for rotation at its opposite ends at the forward set of endsof a pair of laterally spaced, elongated arms 58. The rear ends of arms58 are journaled at points 60 on arms 32. A plurality of identical,laterally spaced clearing elements 64 are secured to shaft 54 and are sopositioned on the shaft that they are out of alignment with diggingelements 40 when viewed from above, as seen in FIG. 3.

Referring again to FIG. 2, each clearing element 64 includes threeclearing teeth 64a, 64b, 640. The teeth on each clearing element haveequal length. Each tooth, and referring specifically to tooth 64a, isarcuate, having a concave forward face 64d. The clearing elements aresubstantially aligned with each other in a direction extending axiallyof the shaft whereby the teeth on the elements are aligned incircumferentially spaced rows extending substantially axially of shaft54.

Secured to shaft 54 adjacent its opposite ends are a pair of laterallyspaced disks 66. Disks 66 are spaced apart a slightly greater distancethan the distance between the outer sides of disks 50 on the digginghead and coact with disks 50 to maintain proper lateral alignment of thedigging and clearing heads. Should one of the heads be urged to movelaterally, disks 66, 50 at one end of the heads would come into contactto prevent lateral relative movement between the heads. This thenprevents the heads from being moved into position where teeth 64 on theclearing head would be in vertical alignment with teeth 40 on thedigging head.

A pair of hydraulic rams 68 are pivotally connected adjacent one set oftheir ends to frame 12, and adjacent their other set of ends to arms 32.Previously-described journal points 36 pivotally mount arms 32 forswinging movement relative to frame 12, whereby the digging head may beraised or lowered relative to the ground. Rams 68 on contraction lowerarms 32, and thus digging head 16, to a lowered, ground-penetratingposition as illustrated in FIG. 1, wherein the teeth of the digginghead, upon rotation, penetrate the ground for picking rocks or otherarticles from below the surface. Extension of rams 68 swings arms 32upwardly to raise the digging head above ground level. The rams and armsare actuatable to position the digging head in multiple adjustedpositions between its raised and lowered positions and to secure thedigging head in any of such adjusted positions.

A pair of laterally-spaced motors 70 are mounted adjacent arms 32, withone motor adjacent journal connection 36 for one of arms 32 and theother motor adjacent journal connection 36 for the other arm 32. Theshaft 75 of each motor 70 is substantially aligned with the axis ofrotation for its associated arm 32 at journal point 36.

Motors 70 are drivingly connected to opposite sets of ends of thedigging and clearing heads through drive trains, such as that indicatedgenerally at 74 for one of the motors. Drive train 74 includes a drivesprocket 76 secured to shaft 75, a driven sprocket 78 spaced forwardlytherefrom, and a drive chain 80 trained over sprockets 76, 78. Sprocket78 is secured to a shaft 82 which also carries a spur gear 84 andanother sprocket 86. A sprocket 88 shown in dashed outline in FIG. 2, issecured to shaft 30 of the digging head and a drive chain 90 is trainedaround sprockets 86, 88. Motor 70 thus is drivingly connected to thedigging head through drive chains 80, 90 and sprockets 76, 78, 86, and88.

The teeth of spur gear 84 engage the teeth of another spur gear 94. Gear94 is secured to a rotatable shaft 96 substantially aligned with theaxis of rotation for arm 58 at journal point 60. Also secured to shaft96 is a sprocket 100. A sprocket 102 (shown in dashed outline in FIG. 2)is secured to shaft 54 of the clearing head and a drive chain 104 istrained around sprockets 100, 102. Motor 70 thus is drivingly connectedto the clearing head through drive chains 80, 104, sprockets 76, 78,100, 102, and gears 84, 94.

The drive train just described is operable, on actuation of motor 70, toproduce rotation of the digging head and clearing head in oppositedirections relative to each other. The digging head rotates in aclockwise direction as viewed in FIGS. 1 and 2, whereby its diggingteeth on passing under shaft 30 move forwardly of the apparatus. Theclearing head rotates in a counterclockwise direction as viewed in FIGS.1 and 2,

whereby its teeth pass in an arc rearwardly of the apparatus on movingunder shaft 54. With the previously described disposition of theclearing head relative to the digging head, the teeth of clearingelements 64 pass freely between the teeth of digging element 40.

The sprockets and gears in drive train 74 have such dimensions that thedigging and clearing heads are rotated in a predetermined, substantiallyconstant, timed relationship, with the clearing head being rotated morerapidly than the digging head. More specifically, the relativerotational speeds of the clearing and digging heads are in a five tothree ratio. Thus each successive row of clearing teeth on the clearinghead coacts with each successive row of digging teeth on the digginghead, whereby they serve to sweep articles from the trailing edge of arow of digging teeth, as will be described in greater detail below.

Describing now conveyor 20 mounted rearwardly of the digging head, itincludes a pair of elongated laterally spaced side members 110, 112which support a grate structure 114 therebetween. Side members 110, 112have forward portions a, 112a, which are spaced apart laterallysubstantially the width of the clearing and digging heads; portions110b, l12b which converge on progressing rearwardly; and substantiallyparallel portions 110C, 1120 which are more closely spaced. The gratestructure includes a plurality of elongated, laterally spaced, parallelbars 116 which, when viewed from above, extend parallel to portions110c, 112c of the side members. The upper surfaces of bars 116 aresubstantially aligned with each other at a level below the tops of sidemembers 110, 112. As is best seen in FIG. 2, the forward portions ofside membr rs 110, 112 and bars 116 are inclined at a low angle as theyprogress rearwardly from the digging head, and then are inclined at amuch steeper angle farther from the digging head.

Mounted inwardly of and adjacent side members 110, 112, are a pair oflaterally-spaced endless drive chains 120, 122. These chains are trainedover spaced sprockets adjacent the forward and rear ends of bars 116 ofthe grate structure. The chains have upper reaches extendingsubstantially parallel to, but slightly below, the upper surfaces ofbars 116, and lower reaches paralleling and adjacent the lower sides ofbars 116, as is best illustrated in FIG. 2. A pair of vertically spacedguide sprockets, such as those seen in dashed outline in FIG. 2, at 124,126 train intermediate portions of a chain along a side of the gratestructure. The sprockets over which chains 120, 122 are trained at therear end of the grate structure are secured to a drive shaft 130extending laterally of the apparatus. This drive shaft is operativelyconnected to a motor 132 which is accuatable to drive the chains, withthe upper reaches of the chains moving rearwardly of the apparatus.

A plurality of spaced, elongated bars 134 extend between and are securedat their opposite sets of ends to chains 120, 122. Bars 134 are mountedfor sliding movement along the tops of bars 1 16 of the grate structureupon movement of chains 120, 122. Secured to each of bars 134 are aplurality of laterally spaced fingers 138 which project outwardly fromthe bar and away from the grate structure.

Disposed laterally outwardly from opposite sides of chains 120, 122 andadjacent portions 110a, 110b, and 112a, l12b of the side members are aplurality of endless power-driven conveyor belts 144. The upper reachesof belts 144 lie in a substantially common plane with the upper surfacesof grate bars 116.

Describing now the operation of the apparatus to pick rocks or otherarticles from the ground, ram 68 is contracted to lower the digging headinto the groundpenetrating position shown in FIG. 1. On rotation, thedigging teeth will dig into the ground. As the apparatus is drivenforwardly over the ground and the digging head is rotated, the diggingteeth pick rocks, or other articles, from the ground and carry them upand over the shaft of the digging head. The arcuate configuration of theteeth on the digging head serves to hold the rocks in the teeth as thedigging head is rotated. With the digging elements being spaced apartlaterally in the digging head, dirt and smaller articles will fallbetween the teeth and back to the ground.

As the picked articles are passed over the shaft of the digging headthey are swept from the digging teeth by operation of the clearing head.Explaining further, when an article is carried over the digging headshaft by a tooth, such as tooth 40a, it will fall onto the trailing edgeof the preceeding tooth, 40b. The clearing head is rotated in timedrelationship with the digging head, whereby successive rows of clearingteeth coact with successive rows of digging teeth, and the clearingteeth are rotated faster than the digging teeth. A row of clearingteeth, such as that indicated at 64a, will pass between a row of diggingteeth, such as that indicated at 40a, in an are adjacent the trailingedge of digging teeth 40b to sweep articles carried in the regionbetween digging teeth 40a, 40b from the digging head.

Articles cleared from the digging head are discharged onto the forwardend of the grate structure of conveyor 20. As one of bars 134 with itsassociated fingers 138 is moved by the chains over the forward end ofthe conveyor, it engages articles discharged onto the grate structure,and slides them up the grate bars and over the rearwardmost end of theconveyor to dump them into crusher 24. Articles discharged onto belts144 outside chains 120, 122 are conveyed up the conveyor by movement ofthe belts and are moved laterally onto the grate structure by slidingcontact with converging portions 110b, 1l2b of the side members. As thearticles are moved up the conveyor, dirt and other small matter fallsthrough the grate structure to the ground.

The depth of penetration of the digging teeth may be adjusted as desiredby selective adjustment of rams 68 which raise and lower arms 32. Thejournal mountings 60 for the rear ends of arms 58 permit the clearinghead to swing upwardly and away from the digging head. The clearinghead, however, normally is yieldably biased downwardly by gravity towardthe digging head. Should a rock which is too large to be accommodated bynormal coaction of the clearing teeth and the digging teeth be picked upby the digging teeth, the clearing head may raise as the clearing teethengage the top of the rock. The clearing head then merely rides over thetop of the rock. Were the clearing head not able to ride over a rock inthis manner there is a possibility that such would wedge between theteeth and cause substantial damage to the apparatus.

By use of such novel apparatus large land areas may be prepared foragriculture. Explaining further, certain types of crops, for examplepotatoes and sugar beets, require soil which is relatively free ofrocks. This apparatus, provides a rapid and efficient means for removingrocks from the soil, whereby the land may be made usable.

While a specific embodiment of the invention has been described herein,it should be apparent to those skilled in the art that variations andmodifications are possible without departing from the spirit of theinvention.

1. Apparatus for picking rocks or similar articles from the groundcomprising:

A main frame supported for forward movement over the ground,

A rotatable digging head including an elongated central shaft disposedwith its central axis extending transversely of the frame and aplurality of elongated digging teeth secured to and projecting radiallyoutwardly from the shaft, said teeth being spaced laterally from eachother in a direction extending axially of said shaft,

means mounting said digging head for vertical movement to differentadjusted positions relative to said frame between a loweredground-penetrating position, wherein outer ends of the digging teethwill penetrate the ground on rotation of the digging head, and a raisedposition above the ground,

power-operated means for moving said digging head between its differentadjusted positions and for securing said digging head in one of saidselected positions,

a rotatable clearing head including an elongated shaft disposed with itscentral axis extending transversely of the frame and substantiallyparalleling the axis of the shaft of the digging head and a plurality ofelongated clearing teeth secured to and projecting radially outwardlyfrom the shaft, said clearing teeth being spaced laterally from eachother in a direction extending axially of the shaft and having suchwidth and spacing that they may move freely between said digging teethon relative rotation of said heads,

means mounting said clearing head above said digging head for movementtoward and away from said digging head and yieldably biasing saidclearing head into a position where the clearing teeth on being rotatedpass between the digging teeth, said clearing head being adapted to moveaway from said digging head when an unyielding object is interposedtherebetween in such a manner as to produce a force urging the clearinghead away from the digging head, and

driving means for rotating said heads in opposite directions with thedigging teeth moving forwardly of the apparatus on passing under theshaft of the digging head to pick articles and raise them from theground and the clearing teeth moving rearwardly of the apparatus onpassing under the shaft of the clearing head to remove picked articlesfrom the digging teeth as they are raised. by the digging teeth over theshaft of the digging head.

2. The apparatus of claim 1, wherein said driving means comprises meansfor rotating the digging and clearing heads in a predetermined timedrelationship, with a clearing tooth on being rotated below the shaft ofthe clearing head passing through an arc adjacent the trailing edge of adigging tooth rotated over the shaft of the digging head.

3. The apparatus of claim 2, wherein the clearing teeth are disposed ina plurality of circumferentially spaced rows extending substantiallyaxially of the clearing head, the digging teeth are disposed in aplurality of circumferentially spaced rows extending substantiallyaxially of the digging head, said digging head having a greater numberor rows of teeth than said clearing head, and said driving means isoperable to rotate the clearing head faster than said digging head sothat each successive row of clearing teeth coacts with each successiverow of digging teeth to remove picked articles therefrom.

4. The apparatus of claim 3, wherein a digging tooth is arcuate, havinga concave surface facing in the direction of rotation for the digginghead.

5. Apparatus for picking rocks or similar articles from the groundcomprising:

a main frame supported for forward movement over the ground,

a rotatable digging head supported on said main frame adjacent theground including an elongated shaft disposed with its central axisextending transversely of the frame and a plurality of elongated diggingteeth secured to and projecting radially outwardly from the shaft, saidteeth being spaced laterally from each other in a direction extendingaxially of said shaft,

a rotatable clearing head above said digging head including an elongatedshaft disposed with its central axis extending transversely of the frameand substantially parallel to the shaft of the digging head and aplurality of elongated clearing teeth secured to and projecting radiallyoutwardly from the shaft, said clearing teeth being spaced laterallyfrom each other in a direction extending axially of the shaft and havingsuch width and spacing that they may move freely between said diggingteeth on relative rotation on said heads,

means mounting said clearing head on said main frame for movement towardand away from the digging head and yieldably biasing the clearing headinto a position where the clearing teeth on being rotated pass betweenthe digging teeth, said clearing head being adapted to move away fromsaid digging head when an unyielding object is interposed therebetweenin such a manner as to produce a force urging the clearing head awayfrom the digging head, and

driving means for rotating said heads in opposite directions with thedigging teeth moving forwardly of the apparatus on passing under theshaft of the digging head to pick articles and raise them from theground and the clearing teeth moving rearwardly of the apparatus onpassing under the shaft of the clearing head to remove picked articlesfrom the digging teeth as they are raised by the digging teeth over theshaft of the digging head.

6. The apparatus of claim 5, which further comprises means mounting saiddigging head for vertical movement to different adjusted positionsrelative to the frame between a lowered ground-penetrating position,wherein outer ends of the digging teeth will penetrate the ground onrotation of the digging head, and a raised position above the ground,and power-operated means for moving said digging head between its saiddifferent adjusted positions and for securing said digging head in oneof said adjusted positions.

7. The apparatus of claim 6, wherein said means for moving said digginghead and securing it in a selected position comprises a double-actingram.

8. The apparatus of claim 5, which further comprises conveyor meansmounted on said frame rearwardly of said digging and clearing headsontowhich picked articles may be discharged from the digging head, operableto move such articles away from said heads, said conveyor meansincluding an open grate structure having an upper surface for supportingarticles moved away from said heads, spaced conveyor elements projectingupwardly from said upper surface of the grate structure and mounted formovement over said grate structure, and powered means connected to saidconveyor elements for moving them over said grate structure in adirection away from said heads.

9. The apparatus of claim 8, wherein a conveyor element comprises aplurality of elongated, upwardly projecting, spaced fingers.

' 10. The apparatus of claim 5, wherein said driving means comprisesmeans for rotating the digging and clearing heads in a predeterminedtimed relationship, with a clearing tooth on being rotated below theshaft of the clearing head passing through an are adjacent the trailingedge of a digging tooth rotated over the shaft of the digging head toremove picked articles from the digging tooth which have been carriedover the shaft of the digging head.

11. The apparatus of claim 10, wherein the clearing teeth are disposedin a plurality of circumferentially spaced rows extending substantiallyaxially of the clearing head, the digging teeth are disposed in aplurality of circumferentially spaced rows extending substantiallyaxially of the digging head, said digging head having a greater numberof rows of teeth than said clearing head, and said driving means isoperable to rotate the clearing head faster than said digging head sothat each successive row of clearing teeth coacts with each successiverow of digging teeth to remove picked articles therefrom.

12. The apparatus of claim 5, wherein a clearing tooth is arcuate,having a concave surface facing in the direction of rotation for theclearing head.

13. Apparatus for picking rocks or similar articles from the groundcomprising:

a main frame supported for forward movement over the ground,

a rotatable digging head supported on said main frame adjacent theground including an elongated shaft disposed with its central axisextending transversely of the frame and a plurality of elongated diggingteeth secured to and projecting radially outwardly from the shaft, saidteeth being spaced laterally from each other in a'direction extendingaxially of said shaft and disposed in a plurality of circumferentiallyspaced rows extending substantially axially of the digging head,rotatable clearing head supported on said main frame above said digginghead including an elongated shaft disposed with its central axisextending transversely of the frame and substantially parallel to theshaft of the digging head and a plurality of elongated clearing teethsecured to and projecting radially outwardly from the shaft, saidclearing teeth being spaced laterally from each other in a directionextending axially of the shaft and having such width and spacing thatthey may move freely between said digging teeth on relative rotation ofsaid heads and disposed in a plurality of circumferentially spaced rowsextending substantially axially of the clearing head, said clearing headhaving a lesser number of rows of teeth than said digging head, and

driving means operatively connected to said heads head, with saidclearing head rotating faster than said digging head and each successiverow of clearing teeth coacting with each successive row of digging teethand passing through an are adjacent the trailing edge of said row ofdigging teeth to remove picked articles from the digging teeth as suchare raised over the shaft of the digging head, saidclearing head beingadapted to move away from said digging head when an unyielding object'isinterposed therebetween in such a manner as to produce a force urgingthe clearing head away from the digging head. i

1. Apparatus for picking rocks or similar articles from the groundcomprising: A main frame supported for forward movement over the ground,A rotatable digging head including an elongated central shaft disposedwith its central axis extending transversely of the frame and aplurality of elongated digging teeth secured to and projecting radiallyoutwardly from the shaft, said teeth being spaced laterally from eachother in a direction extending axially of said shaft, means mountingsaid digging head for vertical movement to different adjusted positionsrelative to said frame between a lowered ground-penetrating position,wherein outer ends of the digging teeth will penetrate the ground onrotation of the digging head, and a raised position above the ground,power-operated means for moving said digging head between its differentadjusted positions and for securing said digging head in one of saidselected positions, a rotatable clearing head including an elongatedshaft disposed with its central axis extending transversely of the frameand substantially paralleling the axis of the shaft of the digging headand a plurality of elongated clearing teeth secured to and projectingradially outwardly from the shaft, said clearing teeth being spacedlaterally from each other in a direction extending axially of the shaftand having such width and spacing that they may move freely between saiddigging teeth on relative rotation of said heads, means mounting saidclearing head above said digging head for movement toward and away fromsaid digging head and yieldably biasing said clearing head into aposition where the clearing teeth on being rotated pass between thedigging teeth, said clearing head being adapted to move away from saiddigging head when an unyielding object is interposed therebetween insuch a manner as to produce a force urging the clearing head away fromthe digging head, and driving means for rotating said heads in oppositedirections with the digging teeth moving forwardly of the apparatus onpassing under the shaft of the digging head to pick articles and raisethem from the ground and the clearing teeth moving rearwardly of theapparatus on passing under the shaft of the clearing head to removepicked articles from the digging teeth as they are raised by the diggingteeth over the shaft of the digging head.
 2. The apparatus of claim 1,wherein said driving means comprises means for rotating the digging andclearing heads in a predetermined timed relationship, with a clearingtooth on being rotated below the shaft of the clearing head passingthrough an arc adjacent the trailing edge of a digging tooth rotatedover the shaft of the digging head.
 3. The apparatus of claim 2, whereinthe clearing teeth are disposed in a plurality of circumferentiallyspaced rows extending substantially axially of the clearing head, thedigging teeth are disposed in a plurality of circumferentially spacedrows extending substantially axially of the digging head, said digginghead having a greater number or rows of teeth than said clearing head,and said driving means is operable to rotate the clearing head fasterthan said digging head so that each successive row of clearing teethcoacts with each successive row of digging teeth to remove pickedarticles therefrom.
 4. The apparatus of claim 3, wherein a digging toothis arcuate, having a concave surface facing in the direction of rotationfor the digging head.
 5. Apparatus for picking rocks or similar articlesfrom the ground comprising: a main frame supported for forward movementover the ground, a rotatable digging head supported on said main frameadjacent the ground including an elongated shaft disposed with itscentral axis extending transversely of the frame and a plurality ofelongated digging teeth secured to and projecting radially outwardlyfrom the shaft, said teeth being spaced laterally from each other in adirection extending axially of said shaft, a rotatable clearing headabove said digging head including an elongated shaft disposed with itscentral axis extending transversely of the frame and substantiallyparallel to the shaft of the digging head and a plurality of elongatedclearing teeth secured to and projecting radially outwardly from theshaft, said clearing teeth being spaced laterally from each other in adirection extending axially of the shaft and having such width andspacing that they may move freely between said digging teeth on relativerotation on said heads, means mounting said clearing head on said mainframe for movement toward and away from the digging head and yieldablyBiasing the clearing head into a position where the clearing teeth onbeing rotated pass between the digging teeth, said clearing head beingadapted to move away from said digging head when an unyielding object isinterposed therebetween in such a manner as to produce a force urgingthe clearing head away from the digging head, and driving means forrotating said heads in opposite directions with the digging teeth movingforwardly of the apparatus on passing under the shaft of the digginghead to pick articles and raise them from the ground and the clearingteeth moving rearwardly of the apparatus on passing under the shaft ofthe clearing head to remove picked articles from the digging teeth asthey are raised by the digging teeth over the shaft of the digging head.6. The apparatus of claim 5, which further comprises means mounting saiddigging head for vertical movement to different adjusted positionsrelative to the frame between a lowered ground-penetrating position,wherein outer ends of the digging teeth will penetrate the ground onrotation of the digging head, and a raised position above the ground,and power-operated means for moving said digging head between its saiddifferent adjusted positions and for securing said digging head in oneof said adjusted positions.
 7. The apparatus of claim 6, wherein saidmeans for moving said digging head and securing it in a selectedposition comprises a double-acting ram.
 8. The apparatus of claim 5,which further comprises conveyor means mounted on said frame rearwardlyof said digging and clearing heads onto which picked articles may bedischarged from the digging head, operable to move such articles awayfrom said heads, said conveyor means including an open grate structurehaving an upper surface for supporting articles moved away from saidheads, spaced conveyor elements projecting upwardly from said uppersurface of the grate structure and mounted for movement over said gratestructure, and powered means connected to said conveyor elements formoving them over said grate structure in a direction away from saidheads.
 9. The apparatus of claim 8, wherein a conveyor element comprisesa plurality of elongated, upwardly projecting, spaced fingers.
 10. Theapparatus of claim 5, wherein said driving means comprises means forrotating the digging and clearing heads in a predetermined timedrelationship, with a clearing tooth on being rotated below the shaft ofthe clearing head passing through an arc adjacent the trailing edge of adigging tooth rotated over the shaft of the digging head to removepicked articles from the digging tooth which have been carried over theshaft of the digging head.
 11. The apparatus of claim 10, wherein theclearing teeth are disposed in a plurality of circumferentially spacedrows extending substantially axially of the clearing head, the diggingteeth are disposed in a plurality of circumferentially spaced rowsextending substantially axially of the digging head, said digging headhaving a greater number of rows of teeth than said clearing head, andsaid driving means is operable to rotate the clearing head faster thansaid digging head so that each successive row of clearing teeth coactswith each successive row of digging teeth to remove picked articlestherefrom.
 12. The apparatus of claim 5, wherein a clearing tooth isarcuate, having a concave surface facing in the direction of rotationfor the clearing head.
 13. Apparatus for picking rocks or similararticles from the ground comprising: a main frame supported for forwardmovement over the ground, a rotatable digging head supported on saidmain frame adjacent the ground including an elongated shaft disposedwith its central axis extending transversely of the frame and aplurality of elongated digging teeth secured to and projecting radiallyoutwardly from the shaft, said teeth being spaced laterally from eachother in a direction extending axially of said shaft and disposed in aplurality of circumferentiAlly spaced rows extending substantiallyaxially of the digging head, a rotatable clearing head supported on saidmain frame above said digging head including an elongated shaft disposedwith its central axis extending transversely of the frame andsubstantially parallel to the shaft of the digging head and a pluralityof elongated clearing teeth secured to and projecting radially outwardlyfrom the shaft, said clearing teeth being spaced laterally from eachother in a direction extending axially of the shaft and having suchwidth and spacing that they may move freely between said digging teethon relative rotation of said heads and disposed in a plurality ofcircumferentially spaced rows extending substantially axially of theclearing head, said clearing head having a lesser number of rows ofteeth than said digging head, and driving means operatively connected tosaid heads for rotating the same in opposite directions in apredetermined timed relationship, with each row of digging teeth movingforwardly of the apparatus on passing under the shaft of the digginghead to pick articles and raise them from the ground and each row ofclearing teeth moving rearwardly of the apparatus on passing under theshaft of the clearing head, with said clearing head rotating faster thansaid digging head and each successive row of clearing teeth coactingwith each successive row of digging teeth and passing through an arcadjacent the trailing edge of said row of digging teeth to remove pickedarticles from the digging teeth as such are raised over the shaft of thedigging head, said clearing head being adapted to move away from saiddigging head when an unyielding object is interposed therebetween insuch a manner as to produce a force urging the clearing head away fromthe digging head.